Wrong php email form - php

Question

I've already spend hours on this simple code. Email arrives, but fields like name email newsletter are empty. It must be something stupid but it drives me crazzy that it's not working when it's just simple form.
Also, if you know, can you please help me prevent user from clicking on form twice and sending multiple emails. Thank you a lot!
<?php
$name = strip_tags(htmlspecialchars($_GET['name']));
$email_address = strip_tags(htmlspecialchars($_GET['email']));
$message = strip_tags(htmlspecialchars($_GET['message']));
$newsletter = strip_tags(htmlspecialchars($_GET['newsletter']));
// Create the email and send the message
$to = 'xxx#xxx.com';
$email_subject = "Message from from : $name";
$email_body = "Message from form arrived.\n\n"."Message details:\n\nName: $name\n\nEmail: $email_address\n\nPhone: $newsletter\n\nMessage:\n$message";
$headers = "From: form#xxx.com\n";
$headers .= "Reply-To: $email_address";
mail($to,$email_subject,$email_body,$headers);
?>
<form method="GET">
<span>Name</span>
<input type="text" name="name" placeholder="Your name"><br />
<span>E-mail</span>
<input type="email" name="email" placeholder="E-mail"><br />
<div>Message</div>
<textarea type="text" name="message" rows="8" cols="80"></textarea><br />
<input type="checkbox" name="newsletter" id="newsletter">
<label for="newsletter">I wold like to get email infromations</label><br />
<button type="submit">Send</button>
<span class="message"></span>
</form>

Answer 1

You may prefer HEREDOC syntax when working with lengthy strings that include variables, like you would use to generate email content. If your variables are being populated correctly, then this should work.
$email_body = <<<EOT
Message from form arrived.
Message details:
Name: $name
Email: $email_address
Phone: $newsletter
Message:
$message
EOT;